.\"
.\" Copyright (c) 2004 Bruce M. Simpson <bms@spc.org>
.\" Copyright (c) 2004 Darron Broad <darron@kewl.org>
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.Dd August 4, 2009
.Dt IEEE80211_INPUT 9
.Os
.Sh NAME
.Nm ieee80211_input
.Nd software 802.11 stack input functions
.Sh SYNOPSIS
.In net80211/ieee80211_var.h
.Ft void
.Fo ieee80211_input
.Fa "struct ieee80211_node *"
.Fa "struct mbuf *"
.Fa "int rssi"
.Fa "int noise"
.Fc
.Ft void
.Fo ieee80211_input_all
.Fa "struct ieee80211com *"
.Fa "struct mbuf *"
.Fa "int rssi"
.Fa "int noise"
.Fc
.Sh DESCRIPTION
The
.Nm net80211
layer that supports 802.11 device drivers requires that
receive processing be single-threaded.
Typically this is done using a dedicated driver
.Xr taskqueue 9
thread.
.Fn ieee80211_input
and
.Fn ieee80211_input_all
process received 802.11 frames and are designed
for use in that context; e.g. no driver locks may be held.
.Pp
The frame passed up in the
.Vt mbuf
must have the 802.11 protocol header at the front; all device-specific
information and/or PLCP must be removed.
Any CRC must be stripped from the end of the frame.
The 802.11 protocol header should be 32-bit aligned for
optimal performance but receive processing does not require it.
If the frame holds a payload and that is not aligned to a 32-bit
boundary then the payload will be re-aligned so that it is suitable
for processing by protocols such as
.Xr ip 4 .
.Pp
If a device (such as
.Xr ath 4 )
inserts padding after the 802.11 header to align
the payload to a 32-bit boundary the
.Dv IEEE80211_C_DATAPAD
capability must be set.
Otherwise header and payload are assumed contiguous in the mbuf chain.
.Pp
If a received frame must pass
through the A-MPDU receive reorder buffer then the mbuf
must be marked with the
.Dv M_AMPDU
flag.
Note that for the moment this is required of all frames received from
a station and TID where a Block ACK stream is active, not just A-MPDU
aggregates.
It is sufficient to check for
.Dv IEEE80211_NODE_HT
in the
.Vt ni_flags
of the station's node table entry, any frames that do not require reorder
processing will be dispatched with only minimal overhead.
.Pp
The
.Vt rssi
parameter is the Receive Signal Strength Indication of the frame
measured in 0.5dBm units relative to the noise floor.
The
.Vt noise
parameter is the best approximation of the noise floor in
dBm units at the time the frame was received.
RSSI and noise are used by the
.Nm net80211
layer to make scanning and roaming decisions in station mode
and to do auto channel selection for hostap and similar modes.
Otherwise the values are made available to user applications
(with the rssi presented as a filtered average over the last ten values
and the noise floor the last reported value).
.Sh SEE ALSO
.Xr ieee80211 9
